Čьrtъ denotes evil demon across Slavic languages from PIE *(s)ker- 'cut, shorten'. Demons imagined as short, hunchbacked, lame, or asymmetrical. Běsъ means raging demon from Balto-Slavic root for 'fear, terror'. Diabeł borrowed into Polish from Old Czech diábel, adapting Latin diabolus. Pre-Christian spirits absorbed into Christian devil concept. Čьrtъ possibly older euphemism like kusy 'short-tailed'. Bies preserved in folklore and place names like Bieszczady. Licho evolved from 'odd, worthless' to euphemism for devil. Slavic languages retain Indo-European demon terms despite Christian overlay. Čert-ti means 'cut across' in Old Russian. No southern Slavic čьrtъ except Slovene črt 'hatred'.